Comparison of salivary cortisol and calculated free plasma cortisol during low-dose ACTH test in healthy subjects

Objectives: To compare free plasma cortisol (FPC) with salivary and calculated cortisol. Design and methods: FPC, salivary cortisol, free cortisol index (FCI), albumin-derived free cortisol index (FCIalb), Coolen's and Dorin's cortisol were assayed during repeated low-dose ACTH test in healthy women. Results: FPC significantly correlated with its surrogates, the most with FCIalb and salivary cortisol. FPC and salivary cortisol showed the highest method agreement. Conclusions: FCIalb and salivary cortisol are preferred surrogates of FPC. (C) 2010 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.